Prime Minister Anthony Albanese, Governor-General David Hurley and Opposition Leader Peter Dutton marked the monarch's passing with a ceremony at the Queen's Terrace on Saturday morning.
The wreath-laying comes more than 30 years after the monarch opened the new Parliament House in 1988, which included unveiling a statue of herself.
The Queen's eldest son became King Charles III immediately after her death in the early hours of Friday morning at Balmoral Castle in Scotland.
In a speech overnight, the new king promised to serve the crown's realms and territories across the world with "loyalty, respect and love".
"As the Queen herself did with such unswerving devotion, I too now solemnly pledge myself," King Charles said.
Across the country, Australians continue to mark the passing of the Queen, with hundreds of people laying flowers at Government House in Sydney and Melbourne.
On Sunday, a Proclamation of the King ceremony will be held outside Parliament House in Canberra, followed by a 21-gun salute.
On Friday evening, a 96-gun salute took place in the federal parliament forecourt - one round for each year of the life of the Queen, who reigned for 70 years.
The sails of the Sydney Opera House, which Her Majesty opened in 1973, were illuminated in her honour. So too were monuments in other cities, and flags were flown at half mast around the nation.
Since news broke of the monarch's passing Australians have gathered to lay flowers, sign condolence books and raise a glass to the Queen.
Some noted that with the death of the monarch, who reigned for so long that many Australians have known no other head of state, they had lost a signifier of their own lives.
"Even if you're not a thoroughly devoted monarchist, you still recall her events along with our own, and you find that she's a kind of marker for our lives," said John Myers, 70, of Hawthorn in Melbourne's east.
"Now she's gone, we feel a little older, and we feel that loss."
Melburnian Pettifleur Berenger, 57, also said it was hard to imagine life without her.
"She had so much humour and dignity and love for her country and the Commonwealth," Ms Berenger told AAP.
"She was the grandmother of the Commonwealth," Sydneysider Oliver Pasusuwin said.
Mr Hurley and Mr Albanese will fly to London on Thursday to attend the Queen's funeral, the date for which is still to be confirmed.
No official mourning period has been declared in Australia, unlike in the UK which has begun 10 days of mourning.
The NSW, Queensland and federal parliaments have suspended their sitting days next week, while Victorian and West Australian MPs will sit on Tuesday to hear condolence motions.
Also this weekend, the AFL and NRL will observe one minute's silence at all games on Saturday and Sunday, with one-minute silences also expected at cricket and soccer matches on Sunday.
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